The present invention relates generally to a vehicle ventilation device, and more particularly to an automatic ventilation device for controlling the internal temperature of a parked vehicle to prevent it from being overheated on hot days.
The operator and passengers of a vehicle often experience considerable discomfort when they enter a vehicle that has been parked under the hot sun or in a non-cooled garage during hot weather. Although air conditioning technology to cool the passenger compartment is well known, it normally takes some time before the air conditioning is effective to reduce the internal temperature of the compartment to a comfortable level and to cool such components as the steering wheel and hand brake to the point that they can be touched without discomfort. In particularly hot conditions the temperature may reach at least 70xc2x0 C. Such excessively high temperatures not only cause personal discomfort but also may cause damage to interior trim, plastic fixtures and other interior components of the vehicle and to articles that have been left in the vehicle.
Many devices have been proposed for overcoming this problem but none have worked effectively or become popular.
One form of such device includes a cooling unit consisting of a cooling chamber with at least one insulated wall having on opposite sides, a heat sink and a cooling block having there between a thermoelectric chip. The device also includes an air intake conduit, a cool air conduit, and an exhaust conduit and means for supplying power from the vehicle battery to the cooling unit.
A further device is intended to be attached to the side window of the vehicle using an interfacing fixture that is attached between the door frame and the side window. The device includes a housing that has an air outlet port, a DC motor, a centrifugal fan, a voltage polarity switch and a temperature control module. The temperature control module consists of first and second heat exchangers and a Peltier-effect thermoelectric element. Electric power is supplied to the device through a control unit that takes power from the vehicle battery at a pre-selected time.
In yet another approach, the device comprises at least one thermal conductor containing a phase-change working substance for cooling the overheated passenger compartment. The thermal conductor has three sections, namely, an evaporator section located in the vehicle compartment, a condenser section located outside the vehicle and an adiabatic section there between. The heat in the vehicle compartment causes evaporation of the working substance in the evaporator section, which draws heat from the compartment. The resulting difference in vapor pressure between the evaporator section and the condenser section drives the vapor-phase working substance from the evaporator section through the adiabatic section to the condenser section where it condenses, thus releasing the latent heat of condensation to the ambient air. The evaporator section is normally attached to the inner surface of the roof panel and the condenser section is mounted on top of the roof panel.
All these prior devices are relatively complicated and expensive and, especially for the third approach, require modification of the structure of the vehicle. A further problem associated with the powered devices is that power usage is not particularly efficient, which results in battery drain, especially when the device is directly connected to the battery of the vehicle.
An alternative solution to overcome the inconvenience caused by overheating of the passenger compartment of a parked vehicle would therefore be desirable.
This invention provides a device for reducing overheating of the passenger compartment of a parked vehicle, which makes use of existing components of the vehicle, for example, the air conditioner fan, its motor and the associated ducting so as to minimize the number of components required and which incorporates a power management system to reduce or eliminate problems of battery drain.
According to the invention a device for reducing overheating in the passenger compartment of a parked vehicle comprises a temperature sensor, a temperature comparator and a control means, preferably micro-processor based, in electrical communication with the comparator for controlling the actuation and operation of an existing air conditioner fan of a vehicle; the control means incorporating a power supply management means designed to draw energy in pulses from a battery unit of the vehicle to energise the motor when the temperature in the passenger compartment exceeds a pre-determined level, and to cease drawing energy when the temperature falls below the predetermined level,
Preferably, the device incorporates a switch that allows the device to operate only when the ignition of the vehicle is turned off. The switch is preferably designed to operate automatically when the ignition of the vehicle is turned off.
Since the device can only operate efficiently when the air conditioner inlet vents are open, when the vehicle has electrically operated air conditioner vents, the control means preferably is designed to open the inlet vents when it is switched on. If the vehicle does not have electrically operated air conditioner vents, the device may be associated with an attachment for converting the inlet ducts to electrical operation.
The device is provided with connections, preferably jack connections for connecting it directly or indirectly to the battery of a vehicle and to the motor of the ventilator fan and to by-pass the air conditioner fan speed controller. It preferably also has connections to the inlet vents of the vehicle.
The control means preferably employs a pulse width modulation technique to control energy usage from the battery. It is preferred that the pulse frequency of a pulse width modulator is set above the normal audible range and below the RF frequency so as to avoid human discomfort and also to avoid possible frequency related interference to the vehicle including its electronic components and the related devices. It is preferably set at 24 KHz.
The use of a pulse width modulation technique by which the device draws power from the battery for a predetermined time and then automatically ceases to draw power for a minimum predetermined time, which may be the same as or different from the first time, if, or until, the temperature again exceeds the predetermined level, allows the device to remain operable over a very much longer period before the battery would be discharged to an unacceptable level at which the vehicle, can no longer be started.
The device preferably also incorporates a battery condition monitor whereby operation of the system is halted or prevented if the voltage of the battery unit is, or falls below, below an acceptable level. The battery conditioner monitor is preferably associated with a warning light or other indicator to draw attention to the fact that there may be battery problems.
Monitoring battery condition ensures that operation of the device cannot drain the battery to a level below that needed to start the vehicle. Preferably the battery condition monitor prevents operation of the device when the battery voltage drops to a level that is well above the minimum voltage needed to start the vehicle.
Preferably the device is programmed to allow only a fixed number of cycles of drawing and ceasing to draw power before it shuts off, regardless of the temperature inside the compartment at that time and is reset when the vehicle is restarted using the ignition switch.
The control means may employ analog or, more preferably, digital processing techniques for the temperature comparator and battery monitoring functions of the device.
The device of the invention will also normally include a display board or display module which houses the temperature sensor, an on/off switch and an indicator light, preferably an LED, for indicating battery condition.
The display board or module is preferably designed to be mounted unobtrusively on the dashboard of the vehicle with the control means being housed in a module that can be mounted beneath the dashboard.
The invention thus provides a purely electronic solution to the problem of passenger compartment overheating by xe2x80x9cpiggy-backingxe2x80x9d onto existing components of the vehicle. Moreover, by causing cooler outside air to circulate through the air conditioner ducting, not so much heat will be present in the ducting when the air-conditioner system is subsequently turned on since the air-conditioner evaporator coils will be kept cool by the circulated air. In addition, the humidity of the passenger compartment will tend to equilibrated with the humidity outside the vehicle thus reducing damage to vehicle components and other artifacts that are prone to damage by moisture.
The use of the device also produces a deodorizing effect by ensuring that the odours from odiferous vapours are swept out of the vehicle, even when it is parked, and that any odiferous materials that have been accidentally transferred into the vehicle, for example on the shoes of the occupants, and have ceased to smell when they dry do not start to smell again if they are re-moistened by a build-up of humidity in the vehicle.